The present invention is directed to the use of metal chelates as a delivery system to improve the selectivity of 2-(substituted benzoyl)-1,3-cyclohexanedione compounds as post-emergence herbicides in crops.
The protection of crops from weeds and other undesirable vegetation which inhibit crop growth is a constantly recurring problem in agriculture. To help combat this problem researchers in the field of synthetic chemistry have produced an extensive variety of chemicals and chemical formulations effective in the control of such unwanted growth. Chemical herbicides of many types have been disclosed in the literature and a large number are in commercial use.
Unfortunately, many of such herbicides exhibit phytotoxicity to the desired crop as well as to the weeds sought to be controlled. Thus, there is a long-standing need for selective herbicides which will control frequently occurring weeds but which will not adversely affect the crop plants when applied at herbicidally effective levels.
U.S. Pat. Nos. 4,780,127, 4,938,796, 5,006,158 and 5,089,046 disclose 2-(substituted benzoyl)-1,3-cyclohexanedione compounds having the general structure: 
wherein X, Q and Z have the meanings set forth hereinafter. These dione compounds have proved to be effective pre-emergent and postemergent herbicides against a wide variety of grasses, broadleaf weeds and sedges. Moreover, PCT Application No. 97/27748 discloses that metal chelates of 2-(substituted benzoyl)-1,3-cyclohexanedione compounds have proved to be chemically stable for long periods of time under normal as well as extreme temperature conditions.
The parent cyclohexanedione exhibits a substantial phytotoxic effect. In contrast, it has now been discovered that metal chelates of 2-(substituted benzoyl)-1,3-cyclohexanedione compounds will effectively control a broad range of weeds without exhibiting any substantial phytotoxic effect on the crop itself.
The present invention is directed to methods of selectively controlling weeds and other undesirable vegetation in a given crop such as wheat. In one embodiment of this invention, the method comprises the postemergent application of an herbicidally effective amount of a metal chelate of a 2-(substituted benzoyl)-1,3-cyclohexanedione to the locus of such weeds and other vegetation. In another embodiment of this invention, the method comprises the postemergent application of an herbicidally effective amount of a metal chelate of a 2-(substituted benzoyl)-1,3-cyclohexanedione to the locus of such weeds and other vegetation, said metal chelate having been formulated as a microcapsule.
As is employed herein, the term xe2x80x9cherbicidexe2x80x9d is used to denote a compound which controls or modifies the growth of plants. The term xe2x80x9cherbicidally effective amountxe2x80x9d is used to indicate the quantity of such compound which is capable of producing a controlling or modifying effect. Controlling or modifying effects include all deviations from natural development, for example: killing, retardation, leaf burn, albinism, dwarfing, and the like. The term xe2x80x9cplantsxe2x80x9d refers to all physical parts of a plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits.
The present invention relates to the use of metal chelates of herbicidal dione compounds to selectively control weeds and other undesirable vegetation in a given crop such as wheat. These herbicidal dione compounds have the general formula (I): 
wherein X represents a halogen atom; a straight- or branched-chain alkyl or alkoxy group containing up to six carbon atoms which is optionally substituted by one or more groups xe2x80x94OR1 or one or more halogen atoms; or a group selected from nitro, cyano, xe2x80x94CO2 R2xe2x80x94S(O)mR1, xe2x80x94O(CH2)mOR1, xe2x80x94COR2, xe2x80x94OSO2R4, xe2x80x94NR2R3, xe2x80x94SO2NR2R3, xe2x80x94CONR2R3 and xe2x80x94CSNR2R3;
R1 represents a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms;
R2 and R3 each independently represents a hydrogen atom; or a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms;
R4 represents a straight- or branched-chain alkyl, alkenyl or alkynyl group containing up to six carbon atoms optionally substituted by one or more halogen atoms; or a cycloalkyl group containing from three to six carbon atoms;
each Z independently represents halo, nitro, cyano, S(O)mR5, OS(O)mR5, (C1-C6)alkyl, (C1-C6)alkoxy, (C1-C6)haloalkyl, (C1-C6)haloalkoxy, carboxy, (C1-C6)alkylcarbonyloxy, (C1-C6)alkoxycarbonyl, (C1-C6)alkylcarbonyl, amino, (C1-C6)alkylamino, (C1-C6)dialkylamino having independently the stated number of carbon atoms in each alkyl group, (C1-C6)alkylcarbonylamino, (C1-C6)alkoxycarbonylamino, (C1-C6)alkylaminocarbonylamino, (C1-C6)dialkylaminocarbonylamino having independently the stated number of carbon atoms in each alkyl group, (C1-C6)alkoxycarbonyloxy, (C1-C6)alkylaminocarbonyloxy, (C1-C6)dialkylaminocarbonyloxy, phenylcarbonyl, substituted phenylcarbonyl, phenylcarbonyloxy, substituted phenylcarbonyloxy, phenylcarbonylamino, substituted phenylcarbonylamino, phenoxy or substituted phenoxy;
R5 represents cyano; xe2x80x94COR6; xe2x80x94CO2R6; or xe2x80x94S(O)mR7;
R6 represents hydrogen or straight- or branched-chain alkyl group containing up to six carbon atoms;
R7 represents (C1-C6)alkyl, (C1-C6)haloalkyl, (C1-C6)cyanoalkyl (C3-C8)cycloalkyl optionally substituted with halogen, cyano or (C1-C4)alkyl; or phenyl optionally substituted with one to three of the same or different halogen, nitro, cyano, (C1-C4)haloalkyl, (C1-C4 alkyl, (C1-C4)alkoxy or xe2x80x94S(O)mR8;
R8 represents (C1-C4)alkyl, (C1-C4)alkyl substituted with halogen or cyano, phenyl or benzyl;
each Q independently represents C1-C4 alkyl or xe2x80x94CO2R9 wherein R9 is C1-C4 alkyl;
m is zero, one or two;
n is zero or an integer from one to four;
r is one, two or three; and
z is 0 or an integer from 1 to 6.
As used herein, the terms xe2x80x9chalogenxe2x80x9d and xe2x80x9chaloxe2x80x9d include fluorine, chlorine, bromine and iodine atoms. In polyhalogenated groups, the halogens may be the same or different. The term xe2x80x9csubstitutedxe2x80x9d in terms of xe2x80x9csubstituted phenylcarbonyl,xe2x80x9d xe2x80x9csubstituted phenylcarbonyloxy,xe2x80x9d xe2x80x9csubstituted phenylcarbonylaminoxe2x80x9d and xe2x80x9csubstituted phenoxyxe2x80x9d means having one to five substituents, which may be the same or different, selected from the following: halo, nitro, cyano, S(O)mR2, (C1-C6)alkyl, (C1-C6)alkoxy, (C1-C6)haloalkyl, (C1-C6)haloalkoxy, carboxy, (C1-C6)alkylcarbonyloxy, (C1-C6)alkylcarbonyl, (C1-C6)alkoxycarbonyl, (C1-C6)alkylcarbonylamino, amino, (C1-C6)alkylamino and (C1-C6)dialkylamino having independently the stated number of carbon atoms in each group.
The 2-(substituted benzoyl)-1,3-cyclohexanedione compounds of formula I are described, inter alia, in U.S. Pat. Nos. 4,780,127, 4,938,796, 5,006,158 and 5,089,046, the disclosures of which are incorporated herein by reference. Herbicidal 2-(substituted benzoyl)-1,3-cyclohexanedione compounds for use in this invention may be prepared by the methods described in the aforementioned patent publications, or by the application and adaptation of known methods used or described in the chemical literature.
2-(substituted benzoyl)-1,3-cyclohexanedione compounds especially useful in the present invention include those in which z is zero; X is chloro, bromo, nitro, cyano, C1-C4 alkyl, xe2x80x94CF3, xe2x80x94S(O)mR1 or xe2x80x94OR1; n is one or two; and each Z is independently chloro, bromo, nitro, cyano, C1-C4 alkyl, xe2x80x94CF3, xe2x80x94OR1, xe2x80x94OS(O)mR5 or xe2x80x94S(O)mR5. Examples of preferred cyclohexanedione compounds are 2-(2xe2x80x2-nitro-4xe2x80x2-methylsulfonylbenzoyl)-1,3-cyclohexanedione, 2-(2xe2x80x2-nitro-4xe2x80x2-methylsulfonyloxybenzoyl)-1,3-cyclohexanedione and 2-(2xe2x80x2-chloro-4xe2x80x2-methylsulfonylbenzoyl)-1,3-cyclohexanedione.
Compounds of formula (I) may exist in enolic tautomeric forms that may give rise to geometric isomers. Furthermore, in certain cases, the various substituents may contribute to optical isomerism and/or stereoisomerism. All such forms are embraced within compounds useful in the present invention.
Metal chelates of 2-(substituted benzoyl)-1,3-cyclohexanedione compounds of formula I are described, inter alia, in PCT Application No. 97/27748, the disclosures of which are incorporated herein by reference. Metal chelates of 2-(substituted benzoyl)-1,3-cyclohexanedione compounds have the general structure: 
wherein X, Q and Z have the meanings set forth above, and Me represents a di- or trivalent metal ion such as Cu+2, Co+2, Zn+2, Ni+2, Ca+2, Al+3, Ti+3 and Fe+3.
Herbicidal metal chelates of 2-(substituted benzoyl)-1,3-cyclohexanedione compounds for use in this invention may be prepared by the methods described in the aforementioned PCT application, or by the application and adaptation of known methods used or described in the chemical literature.
Metal ions which may be useful in forming the metal chelate compounds of the present invention include di- or trivalent metal ions such as Cu+2, Co+2, Zn+2, Ni+2, Ca+2, Al+3, Ti+3 and Fe+3. The selection of a particular metal ion to form the metal chelate compound will depend upon the dione compound to be chelated and the strength of the metal chelate complex. Without being bound by theory, it appears as if the strength of the metal chelate complex is directly related to the release rate of the triketone from the metal chelate complex, which in turn is related to the selectivity of the metal chelate compounds of this invention. Those skilled in the art will be able to readily determine the appropriate metal ion for use with a specific dione compound without undue experimentation. The preferred metal ions are divalent transition metal ions, particularly Cu+2, Ni+2, Zn+2 and Co+2, with Cu+2 being especially preferred.
Any appropriate salt which would be a source of a di- or trivalent metal ion may be used to form the metal chelate of the dione compound in accordance with this invention. Particularly suitable salts include: chlorides, sulfates, nitrates, carbonates, phosphates and acetates.
It also has been found that the stability and the activity of the herbicidal metal chelate compositions of the present invention is pH dependent. The pH of the metal chelate compositions should be between about 2 and about 10, preferably between about 3 and about 7. Generally, it is believed that for Cu+2 chelate compositions the pH should be between about 4 and 6; for Co+2 between about 3 and 5; and for Ni+2 and Zn+2 about 5. The optimum pH for a particular metal chelate composition can be determined using routine experimental techniques.
The metal chelate of the herbicidal 2-(substituted benzoyl)-1,3-cyclohexanedione compounds can be formulated in the same manner in which herbicides are generally formulated. The choice of formulation and mode of application for any given herbicidal compound may affect its activity, and selection must be made accordingly. Herbicidal compositions may thus be formulated as water dispersible granules, as wettable powders, as powders or dusts, as suspensions, or as controlled release forms such as microcapsules. The formulation of the metal chelate of the herbicidal 2-(substituted benzoyl)-1,3-cyclohexanedione compounds for use in this invention may be prepared by the methods described in the aforementioned patent application or by the application and adaptation of known methods used or described in the chemical literature. Processes for microencapsulating the herbicidal composition specifically have been described in U.S. Pat. Nos. 4,285,720 and 4,956,129 and U.S. application Ser. No. 08/354,409, and may also be prepared by the application and adaptation of known methods used or described in the chemical literature. The object of the formulation, however, is to apply the compositions to the locus where control is desired by a convenient method (i.e., postemergent application). The xe2x80x9clocusxe2x80x9d is intended to include soil, as well as established vegetation.
Formulations containing the metal chelates of the herbicidal dione compounds of formula (I) can be applied by conventional methods to the areas where control is desired. The formulations containing an herbicidal metal chelate according to the invention can also be produced as premixes with other herbicides, or can be tank-mixed with one or more additional herbicidal or other agricultural compositions. Specific examples of other herbicides which may be incorporated in an herbicidal formulation with the metal chelates according the invention include acetanilides, tralkoxydim, bromoxynil and its esters, thiafluamide, MCPA and its esters, 2,4-D and its esters, and fluroxypyr meptyl.
In the practice of the present invention, the metal chelate of the herbicidal 2-(substituted benzoyl)-1,3-cyclohexanedione compounds is applied postemergent to the locus of the undesirable vegetation to be controlled. Application rates will depend on the particular plant species and degree of control desired. In general, application rates of between about 5 and about 500 g/ha may be employed.